//https://leetcode-cn.com/problems/invert-binary-tree/
//翻转二叉树
//给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。

struct TreeNode* invertTree(struct TreeNode* root) {
    if(root == NULL)
    return NULL;

    invertTree(root->left);
    invertTree(root->right);
    struct TreeNode* temp = root->left;
    root->left = root->right;
    root->right = temp;
    return root;
}